Polyhydric alcohol is utilized as a raw material of a synthetic resin and a surfactant, a high boiling point solvent, and a material of antifreeze. The polyhydric alcohol has excellent moisture retaining property and antibacterial property and has a function to repair a hair cuticle. Therefore, the polyhydric alcohol is widely used as a feeling improver for improving spread and slip of a moisturizing agent and cosmetics.
In such an intended use of the polyhydric alcohol, the polyhydric alcohol having higher purity is desired in order to prevent the problems of coloration, performance deterioration and generation of offensive odor due to contamination of impurities.
Numerous methods are known as a synthesis example of a polyhydric alcohol. As one example, a method of reducing hemiacetal such as 2-hydroxy-4-methyltetra-hydroxypyrane or 2-hydroxytetrahydrofuran is known (see Patent Documents 1 to 5).
In Patent Document 1,3-methylpentane-1,5-diol is synthesized by a hydrogenation reaction of 2-hydroxy-4-methyltetrahydropyrane. In this synthesis, it is known that an acetal compound (hereinafter referred to as “MPAE”) represented by the following formula (2) is by-produced.

MPAE has a boiling point close to that of 3-methylpentane-1,5-diol, and is therefore difficult to separate by distillation. This causes decrease of yield from the standpoint of the separation of 3-methylpentane-1,5-diol. For this reason, in conducting a hydrogenation reaction of 2-hydroxy-4-methyltetrahydropyrane, a method of suppressing the amount of MPAE as a by-product by a method of using molybdenum-modified Raney nickel as a hydrogenation catalyst (Patent Document 2) or a method of hydrogenating in the presence of a basic compound (Patent Document 3) is proposed.
Furthermore, it is indicated in Patent Documents 2 and 3 that in a hydrogenation reaction of 2-hydroxy-4-methyltetrahydropyrane, β-methyl-δ-valero-lactone (hereinafter referred to as “MVL”) represented by the following formula (3)
is by-produced, and a suppression method of its formation is proposed.
On the other hand, in Patent Documents 4 and 5, in order to remove 2-(4-hydroxybutoxy)tetrahydrofuran, which is by-produced in the production of 1,4-butanediol by a hydrogenation reaction of a hydroformylated product (2-hydroxytetrahydrofuran) of allyl alcohol and is difficult to separate from 1,4-butanediol by distillation, a method of conducting hydrogenation in the presence of water is proposed.